The general procedure for the synthesis of 4-bromo-3-nitrobenzoic acid from 4-bromobenzoic acid is as follows:
1. prepare a nitration mixture by slowly adding fuming nitric acid (12.4 mL, 0.3 mol) to concentrated hydrochloric acid followed by sulfuric acid (30.1 mL, 0.6 mol) at 0-5 °C.
2. the cooled nitrification mixture was transferred to a beaker fitted with a mechanical stirrer and a charging funnel.
3. 4-Bromobenzoic acid (40 g, 0.2 mol) was slowly added to the nitrification mixture in batches while maintaining a temperature of 0-5°C. The dosing process lasted for 5 hours.
4. After completion of the addition, the reaction mixture was continued to be stirred at room temperature for 2 hours.
5. The reaction mixture was slowly poured into ice water to precipitate the solid product.
6. The solid product was separated by filtration, washed with water to neutrality and subsequently air dried to constant weight to give the pure 4-bromo-3-nitrobenzoic acid (white solid, 47.2 g, 96% yield).
Product characterization data:
1H NMR (300 MHz, CDCl3): δ 7.85 (d, J = 12.0 Hz, 1H), 8.09 (d, J = 12.0 Hz, 1H), 8.48 (s, 1H).
13C NMR (75 MHz, CDCl3): δ 124.2, 132.1, 135.2, 138.0, 139.8, 159.8, 171.0.
